Well Arnold is head of the Executive branch. And in most state governments, the Executive branch does the arresting and the prosecuting.
The question I have is, isn't there someone else in charge of the state police which can arrest these people and charge them with violating the State code? Is that the AG? or is it someone else?
Not everything "in a state code" is a CRIME to violate. Crimes have to be defined as such. For example, if tax code says "only one house can be claimed as a deduction," it's not a CRIME to do so, unless some other CRIMINAL code says so, or says "Any errors on the tax form are a CRIME."
SO, even if the marriages are as phony as a 3-dollar bill (and I think they are), there is nothing that I know of that says "It is a a crime to give out bad marriage certificates." If there is, then maybe the COunty DA (A very liberal Dem, separately elected) would have a basis to prosecute, but Arnold does not control the COunty DA's.